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Abstract

As the most accurate model for simulating light propagation in heterogeneous tissues, Monte Carlo (MC) method has been widely used in the field of optical molecular imaging. However, MC method is time-consuming due to the calculations of a large number of photons propagation in tissues. The structural complexity of the heterogeneous tissues further increases the computational time. In this paper we present a parallel implementation for MC simulation of light propagation in heterogeneous tissues whose surfaces are constructed by different number of triangle meshes. On the basis of graphics processing units (GPU), the code is implemented with compute unified device architecture (CUDA) platform and optimized to reduce the access latency as much as possible by making full use of the constant memory and texture memory on GPU. We test the implementation in the homogeneous and heterogeneous mouse models with a NVIDIA GTX 260 card and a 2.40GHz Intel Xeon CPU. The experimental results demonstrate the feasibility and efficiency of the parallel MC simulation on GPU.

Figures (7)

Tissue structure in MOSE. Tissue 1 is the outermost tissue, Tissue 2 and 3 are both the internal tissues. Shape 1 is the boundary between Tissue 1 and ambient medium and corresponding to Tissue 1. Shape 2 is the boundary between Tissue 1 and Tissue 2 and corresponding to Tissue 2, so do Shape 3.

(a) 3D view of the tissue surface which is projected onto the 2D plane grid. Points A and B are the starting and end points of a step (marked with blue color), respectively. A is the external point of the tissue and B is internal point of the tissue. (b) 2D view of the grid and the projections of the tissue and the photon path, A´ and B´ are the projections of points A and B, respectively. The grid cells intersected with the projection of the photon path are marked with red color.

3D surface rendering of the tissues used in the experiments. The bounding box of the mouse phantom is 38 × 99.2 × 20.8 (mm). The point light source is located near the stomach marked with green color and its coordinate is (20, 50, 15) (mm). The picture is obtained from MOSE.

(a) Speedup varies with the number of threads. (b) Speedup varies with the number of triangle meshes. (c) Speedup varies with the number of tissues. (d) Relative errors between the transmittances obtained from CPU and GPU.